Media transport system for non-contacting printing

Abstract

A digital printing system for printing on a continuous web of print media includes a support structure that guides the continuous web of print media under tension through the printing system. The printing system includes a first mechanism that is affixed to the support structure that positions the print media in a cross track direction. A second mechanism is affixed to the support structure that sets tension of the print media. A third mechanism is affixed to the support structure that sets an angular trajectory of the print media. A roller is affixed to the support structure and is configured to align to the print media being guided through the printing system without necessarily being aligned to another roller located upstream or downstream relative to the roller. A drive roller is affixed to the support structure that moves the print media through the printing system. A printhead is located downstream relative to the first mechanism. The printhead is configured to selectively moisten at least a portion of the print media being guided through the printing system without contacting the print media.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]Reference is made to commonly-assigned copending U.S. patent application Ser. No. ______ (Docket No. 95529) filed ______ entitled “MODULAR MEDIA TRANSPORT SYSTEM”, by DeCook et al.FIELD OF THE INVENTION[0002]The present invention generally relates to printing apparatus for web media and more particularly relates to a printing apparatus having an arrangement of components that do not require precision alignment for feeding a continuous web of media from a supply through one or more printing sections and to a take-up section.BACKGROUND OF THE INVENTION[0003]Continuous web printing allows economical, high-speed, high-volume print reproduction. In this type of printing, a continuous web of paper or other substrate material is fed past one or more printing subsystems that form images by applying one or more colorants onto the substrate surface. In a conventional web-fed rotary press, for example, a web substrate is fed through one or more impr...

AI Technical Summary

Benefits of technology

[0013]One advantage of the present invention is that it allows the web media transport components to self-align to the continuously moving web in order to maintain registration of the printing media. Another advantage of the present invention is that it allows non-contact printing or, more generally, the application of fluid onto the media surface at high speeds, without applying an over-constraining force or pressure that might inadvertently damage the media, cause image misregistration, or otherwise inhibit proper drying or curing of applied inks and other fluids.

Problems solved by technology

Typical of conventional web handling subsystems are heavy frame structures, precision-designed components, and complex and costly alignment procedures for precisely adjusting substrate transport between components and subsystems.

The problem of maintaining precise and repeatable web registration and transport becomes even more acute with the development of high-resolution non-contact printing, such as high-volume inkjet printing.

Variability in ink or other liquid amounts and types and in drying time can cause substrate stiffness and tension characteristics to vary dynamically over a range for different types of substrate, contributing to the overall complexity of the substrate handling and registration challenge.

Problems with such a conventional approach include significant cost in design, assembly, and adjustment and alignment of web handling components along the media path.

While such a conventional approach may allow some degree of modularity, it would be difficult and costly to expand or modify a system with this type of design.

Each “module” for such a system would itself be a complete printing apparatus, or would require a complete, self-contained subassembly for paper transport, making it costly to modify or extend a printing operation, such as to add one or more additional colors or processing steps, for example.

It would be difficult and costly to employ such a solution with a print medium whose stiffness and tension vary during printing, as described above.

Other solutions for web (or belt as referred to above) steering are similarly intended for endless webs in electrophotographic equipment but are not readily adaptable for use with paper media.

Steering using a surface-contacting roller, useful for low-speed photographic printers and taught in commonly assigned U.S. Pat. No. 4,795,070 entitled “Web Tracking Apparatus” to Blanding et al. would be inappropriate for a surface that is variably wetted with ink and would also tend to introduce non-uniform tension in the cross-track direction.

Other solutions taught for photographic media, such as those disclosed in commonly assigned U.S. Pat. No. 4,901,903 entitled “Web Guiding Apparatus” to Blanding are well suited to photographic media moving at slow to moderate speeds but are inappropriate for systems that need to accommodate a wide range of medias, each with different characteristics, and transport each media type at speeds of hundreds of feet per minute.

Images